When the proper operation of an electric installation e.g. a protective installation is to be checked, it is necessary to carry out a number of operations in a well-determined order. An example of a protective device is that which comprises:
A current transformer supplying an image of the line current of the protected devices, a device for measuring this image current and a trigger circuit operating if the measurement of the image current exceeds a threshold. It is necessary, in order to check the trigger circuit to:
(A) Inhibit the trigger circuit;
(B) Short-circuit the current transformer;
(C) Open the current measuring circuit;
(D) Connect the trigger and current measuring circuits to a test equipment.
These various phases of the checking operation must be carried out successively.
Devices have already been proposed which comprise a blade contact box which is connected to the installation to be checked and in which test plugs designed to break some contacts and to establish others for test purpose can be fitted.
But this type of contact is fragile and can become dirty and hence lead to faulty operation.
One aim of the invention is to produce a device enabling the testing of all types of protection without disturbing the operation of the installation. Another aim of the invention is to produce a device which is equipped with contact parts having high specific pressures, which are insensitive to foreign bodies which may enter the test device; they ensure excellent operation of the test device as well as avoiding any disturbance in the installation to be checked itself.